Lipid based foam

ABSTRACT

The present invention relates generally to the field of foams. One aspect of the invention provides a foam having a continuous lipid phase and a porosity of between 1 and 80% wherein, at a temperature at which the lipid phase has a solid lipid content between 0.1 and 80% the foam comprises gas bubbles having at least 50% of their surface occupied by crystals comprising triglycerides. Further aspects of the invention are a product comprising a foam and a process for forming a foam.

FIELD OF THE INVENTION

The present invention relates generally to the field of foams. Oneaspect of the invention provides a foam having a continuous lipid phaseand a porosity of between 1 and 80% wherein, at a temperature at whichthe lipid phase has a solid lipid content between 0.1 and 80% the foamcomprises gas bubbles having at least 50% of their surface occupied bycrystals comprising triglycerides. Further aspects of the invention area product comprising a foam and a process for forming a foam.

BACKGROUND OF THE INVENTION

Lipid foams are of particular interest to the consumer productsindustry, having the potential to provide new textures and sensoryproperties for food and nutrition products as well as in cosmeticproducts. In food products there is increasing concern about the amountof fat consumed in people's diet. Foaming lipids provides a method tomaintain product volume whilst reducing the fat content.

The major difficulty in generating stable foam structures withinlipid-based systems as compared to water-based systems lies in the lackof suitable surfactants for forming stable interfaces between air andlipid. Those surfactants which have been proposed may not be suitablefor stabilizing edible foams due to toxicity or unpleasant taste. As aconsequence, the most common approach for obtaining stable foams in alipid-based matrix is by forming a rigid network in the bulk material,for example by forming a rigid network of crystals in a liquid lipidcontinuous phase or by rapidly cooling the lipid so as to solidify thebulk material. As well as affecting the texture in a way which may notalways be desired, both of these approaches lead to constraints whenprocessing the foam. Having a rigid network in the liquid lipidcontinuous phase affects the ability of the foam to be pumped,deposited, or mixed with other components without destroying thestabilizing network leading to coalescence of bubbles. A foam stabilizedby solidifying the bulk is generally unstable before solidification andso can only be maintained as a foam for a short period and cannot besubject to substantial shear forces during processing.

Hence, there is a need in the industry to find better solutions toproduce stable lipid foams, in particular edible lipid foams which tastegood and are made from natural ingredients. An object of the presentinvention is to improve the state of the art and to provide an improvedsolution to overcome at least some of the inconveniences described aboveor at least to provide a useful alternative. Any reference to prior artdocuments in this specification is not to be considered an admissionthat such prior art is widely known or forms part of the common generalknowledge in the field. As used in this specification, the words“comprises”, “comprising”, and similar words, are not to be interpretedin an exclusive or exhaustive sense. In other words, they are intendedto mean “including, but not limited to”. The object of the presentinvention is achieved by the subject matter of the independent claims.The dependent claims further develop the idea of the present invention.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides in a first aspect a foamhaving a continuous lipid phase and a porosity of between 1 and 80%wherein, at a temperature at which the lipid phase has a solid lipidcontent between 0.1 and 80%, the foam comprises gas bubbles having atleast 50% of their surface occupied by crystals comprisingtriglycerides. In a second aspect, the invention relates to a productcomprising the foam of the invention. A third aspect of the inventionrelates to a process for forming a foam, the process comprising thesteps of providing a composition comprising triglycerides and having alipid content greater than 20 wt. %; controlling the temperature of thecomposition such that the composition comprises triglyceride crystals,has a solid lipid content between 0.1 and 80% and forms a gel; andaerating the gel to form a foam.

It has been surprisingly found by the inventors that, by cooling aliquid lipid composition comprising triglycerides to a temperature atwhich there is partial crystallization and a gel is formed and thenwhipping the composition, a stable foam is produced. The gas bubbles inthe foam were found to be coated in triglyceride crystals. By using aprocess of prolonged and intensive whipping, very stable assemblies ofcrystal-wrapped bubbles can be obtained. The crystals jam togetheraround the bubble, leading to mechanical stability and resisting bubbleshrinkage. The bulk remains soft, e.g. there is no rigid network ofcrystals in between the bubbles. The foam can be diluted with additionaloil and still remain stable (unless so much oil is added that itdissolves the crystals). The foam may be further cooled such that thecontinuous phase solidifies, but if the foam is re-heated and thecontinuous phase re-melts, the stable crystal-wrapped bubbles remainuntil the temperature is raised to the point where all crystals melt (orsubstantially all crystals melt). The foams according to the inventiondo not easily destabilize under mechanical processing, unlike manyparticle-stabilized foams or conventional surfactant stabilized foams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a differential scanning calorimeter crystallization andmelting trace for 20 wt. % cocoa butter in high oleic sunflower oil.

FIG. 2 shows the evolution of rheological properties during gelation ascooling is applied from fully melted state down to 5° C., for 20% cocoabutter in HOSFO.

FIG. 3 shows a 20 wt. % cocoa butter in high oleic sunflower oil foam,prepared as described in example 1, trial 1.2, after 7 days of storage.

FIG. 4 shows a 20 wt. % cocoa butter in high oleic sunflower oil foam,prepared as described in example 1, trial 1.3, after 7 days of storage.

FIG. 5 is a micrograph of 20 wt. % cocoa butter in high oleic sunfloweroil foam, prepared as described in example 1, trial 1.5, showing theabsence of shape relaxation in the dense layer of crystals adsorbed atthe surface of the bubbles.

FIG. 6 is a schematic illustration of the absence of shape relaxationaround a bubble.

FIG. 7 is a polarized optical micrograph of a foam of 20 wt. % highmelting palm fraction in high oleic sunflower oil.

FIG. 8 is a polarized optical micrograph of a foam of 20 wt. % highmelting palm fraction in high oleic sunflower oil, diluted by a factorof around 5.

FIG. 9 is a micrograph of a foam consisting of high oleic sunflower oiland cocoa butter improver

FIG. 10 is a further micrograph of the foam shown in FIG. 9

FIG. 11 is a polarized optical micrograph of a foam containing higholeic sunflower oil and cocoa butter equivalent

DETAILED DESCRIPTION OF THE INVENTION

Consequently the present invention relates in part to a foam having acontinuous lipid phase and a porosity of between 1 and 80%, for examplebetween 10 and 75%, wherein, at a temperature at which the lipid phasehas a solid lipid content between 0.1 and 80%, for example between 0.1and 60%, for example between 0.5 and 40%, for example between 1 and 20%,for example between 5 and 20%, the foam comprises gas bubbles having atleast 50% of their surface occupied by crystals comprisingtriglycerides. A foam is a dispersion of a gas in a solid or liquidmedium. The gas may be any gas commonly used for foam generation such asCO₂, N₂ or N₂O, but typically the gas is air. The term porosity refersto the fraction of the volume of gas-filled voids over the total volume,as a percentage between 0 and 100%. The lipid phase of the foam maycomprise lipidic solids, semisolids or liquids. The lipid phase of thefoam may comprise water-insoluble esters of glycerol with fatty acids.Triglycerides, also called triacylglycerols or triacylglycerides, areesters derived from glycerol and three fatty acids. The temperature atwhich the lipid phase has a solid lipid content between 0.1 and 80% maybe measured by any methods well known in the art. For example the solidlipid content at different temperatures may be measured by pulsed NMR,for example according to the IUPAC Method 2.150. The solid lipid contentat different temperatures may also be measured by differential scanningcalorimetry. The result of a measurement of solid lipid content iscommonly referred to as the solid fat content. Although it is possibleto obtain solid lipid contents intermediate between 0 and 100% with apure triglyceride composition by exploiting the kinetics ofcrystallization and heat transfer, in general it is preferable that thelipid phase comprises a mixture of different triglycerides withdifferent melting points. Indeed, pure triglycerides are expensive andso are not preferred. All components of the foam may be edible. The term“edible” refers to substances which can be eaten safely. Whilst thecurrent invention is not limited to substances permitted for consumptionin any particular jurisdiction, edible compositions may for examplecomprise materials approved for human consumption by the U.S. Food andDrug Administration.

The foam of the invention may have a low moisture content, for examplethe foam may contain less than 5% water by weight, for example less than2.5% water by weight. It should be noted that the foam of the presentinvention can be formed without moisture, for example without the use ofsurfactants in water or the formation of an emulsion containing water.Food ingredients that are completely free from moisture are rare, butthe foam of the invention may be essentially free from water.

The percentage of the gas bubbles' surface occupied by crystals may bemeasured using microscopy (for example optical and/or confocalmicroscopy), coupled with suitable image analysis techniques. With ahigh level of surface coverage it may be immediately obvious afterinspection by microscopy that at least 50% of the surface of the gasbubbles is occupied by crystals.

The crystals occupying at least 50% of the surface of the gas bubblesjam together, resisting any shrinkage of the bubbles and providing astable, flowable foam when the continuous phase is fluid, such as whenthe lipid phase has a solid lipid content between 0.1 and 80%. Thecrystals occupying at least 50% of the surface of the gas bubbles maycause the bubbles to have a non-relaxing shape when the foams arediluted with oil. In the context of the present invention the termflowable foam refers to a foam which can be processed in pumping orstirring units using typical food process equipment without undergoingobvious structural coarsening or collapse. The flowable foam may beflowable under gravity after stirring (for example at 20° C.).

The fat-based confectionery material may comprise gas bubbles havingtheir surface occupied by triglycerides, for example triglyceridecrystals, such that their surface density is at least 15 mg·m⁻², forexample at least at least 25 mg·m⁻², for example at least 50 mg·m⁻², forfurther example at least at least 200 mg·m⁻². The surface density oftriglycerides at the surface may be measured by diluting foams by oiladdition and gentle manual stirring. The samples are then left to atrest until phase separation occurred between an upper layer formed bybubble accumulation, due to buoyancy mismatch between air and thecontinuous oil phase, and a bottom phase formed by oil and the remainingnon-adsorbed triglyceride crystals. The upper foam layers are thencarefully removed and the subnatants are collected for analysis. Theconcentration of triglycerides can be determined by gas-chromatography.From the initial concentration of triglycerides in the material beforewhipping (the gel) and the measured concentration in the supernatant,the interfacial area can be calculated:

-   -   Interfacial area (S) developed by a foam:

$S = \frac{6\varnothing \; V}{D}$

V: volume of foam (m³)φ: porosityD: bubble Sauter diameter (m) as measured by opticalmicroscopy/tomography

-   -   OR/porosity: The levels of aeration may be estimated by Over-Run        (OR) or porosity (φ) measurements in standardized plastic cups.

${\% {OR}} = {\frac{m_{{non}\mspace{14mu} {aerated}} - m_{aerated}}{m_{aerated}} \times 100}$${\% \varnothing} = {\frac{OR}{{OR} + 100} \times 100}$

Concentration of Adsorbed Triglycerides at Interface:

c _(ads) =c _(ini) −c _(non-ads) ×X

C_(ads): glyceride concentration, relative to the oil phase, adsorbed atthe air-oil interface of the bubblesC_(ini): initial concentration of glyceride in the gelC_(non-ads): non-adsorbed glyceride concentration as titrated from thediluted subnatantX: dilution factor applied to the foam before collecting the subnatant

Adsorption Surface Density:

$\Gamma = \frac{{c_{ads}\left( {1 - \varphi} \right)}V}{S}$

The foam of the invention has a number of advantages. At temperatureswhere the continuous phase is fluid the foam's stability makes it easyto process without damaging the foam. The composition of the foam may beadjusted so that there is a high proportion of liquid lipid at thetemperature at which the foam is used, and this allows for soft textureswhile maintaining good stability. The inventors were surprised to findthat the foam remains stable (at rest and during processing) whencombined with other materials, for example other food materials such asproteins, emulsifiers and solid particles.

The foam may be cooled such that the continuous lipid phase is no longerfluid. However, a characteristic of the foam is that, at a temperatureat which the lipid phase has a solid lipid content between 0.1 and 80%,for example after re-heating, the foam still comprises gas bubbleshaving at least 50% of their surface occupied by crystals comprisingtriglycerides. This is in contrast to foams which are simply stabilizedby crystallizing the bulk. A high proportion of the lipid crystals inthe foam of the invention occupy the surface of the gas bubbles at atemperature at which the lipid phase has a solid lipid content between0.1 and 80%. For example, at least 50% by volume of the bubbles may haveat least 50% of their surface occupied by crystals comprisingtriglycerides. The lipid phase may comprise fats such as coconut oil,palm kernel oil, palm oil, cocoa butter, butter oil, lard, tallow,oil/fat fractions such as lauric or stearic fractions, hydrogenatedoils, and blends thereof as well as sunflower oil, rapeseed oil, oliveoil, soybean oil, fish oil, linseed oil, safflower oil, corn oil, algaeoil, cottonseed oil, grape seed oil, nut oils such as hazelnut oil,walnut oil, rice bran oil, sesame oil, peanut oil, palm oil, palm kerneloil, coconut oil, and emerging seed oil crops such as high oleicsunflower oil, high oleic rapeseed, high oleic palm, high oleic soybeanoils & high stearin sunflower or combinations thereof. For example, thelipid phase may comprise fats selected from the group consisting ofcocoa butter, shea butter, illipe butter, sal fat, kokum butter, mangokernel fat, palm oil, coconut oil, soybean oil, rapeseed oil, cottonseedoil, sunflower oil, safflower oil, olive oil and hydrogenation products,inter-esterification products, fractions and combinations of these.

It is advantageous that the foam is stabilized by triglyceride crystalsas these have good consumer acceptance, for example in food products. Ata temperature at which the lipid phase has a solid lipid content between0.1 and 80%, the foam may comprises gas bubbles having at least 50% oftheir surface occupied by triglyceride crystals. The lipid phase maycomprise at least 60 wt. % triglycerides, for example at least 75 wt. %triglycerides, for example at least 90 wt. % triglycerides.

It is beneficial to be able to stabilize a foam having a continuouslipid phase without needing to use triglycerides with high chain lengthfatty acids. Such high chain length fatty acids, especially saturatedones, affect the organoleptic properties of the foam, giving a heavy andwaxy mouthfeel. The inventors were surprised to find that foamsaccording to the invention could be effectively stabilized without usingtriglycerides with high chain length fatty acids, for example by usingthe process of the invention. The gas bubbles comprised within the foamof the invention may have their surface occupied by triglycerides all ofwhose fatty acids have a carbon chain length less than 22. The gasbubbles comprised within the foam of the invention may have theirsurface occupied by triglycerides all of which have an average fattyacid chain length less than 20. For example, the triglyceridepalmitic-oleic-stearic (POSt) has an average chain length of 17.3 aspalmitic acid is C16, oleic acid is C18 and stearic acid is C18.

The foam of the invention may contain more than 95% by weight of totallipids (for example more than 98%, for further example more than 99%) oftriglycerides all of whose fatty acids have a carbon chain length lessthan 22. The foam of the invention may contain more than 95% by weightof total lipids (for example more than 98%, for further example morethan 99%) of triglycerides all of whose fatty acids have an averagechain length less than 20.

The crystallization behaviour of the lipid phase may be examined usingdifferential scanning calorimetry (DSC), a technique in which thedifference in the amount of heat required to increase the temperature ofa sample and reference is measured as a function of temperature. Forexample, a sample comprising the lipid phase may be heated to completelymelt all the lipid, cooled to record the crystallization signature andthen reheated to record the melting signature. When the cooling protocolbrings the mixture so low in temperature that the system solidifies inbulk then the lipid phase in the foam of the current invention may showat least two distinct endothermic melting “peaks” during the reheatingphase, the at least two endothermic melting “peaks” being separated byat least 10° C., for example at least 15° C., for example at least 20°C. The area under each of the at least two peaks may be at least 10% ofthe area under all peaks in the melting trace. Depending on the DSCequipment used, endothermic heat flows may be shown as positive ornegative peaks.

The inventors have found that good results may be obtained using a fator blend of fats having a broad range of crystallization temperatures.Such fats or blends of fats have broad ranges of crystallization peakswhen measured in a differential scanning calorimeter (DSC). These broadranges of crystallization temperatures allow flexibility in selecting atemperature at which the lipid phase has a solid lipid content between0.1 and 80% (for example between 0.1 and 60%, for example between 0.5and 40%, for example between 1 and 20%, for example between 5 and 20%)before aerating the composition to form a foam. DSC measurements of fatsare conveniently carried out between 80° C. and −20° C. The lipid phasein the foam of the invention may have at least 80% of its totalcrystallization enthalpy between 80° C. and −20° C. occurring in atemperature range of at least 20° C., for example a range of at least30° C. The lipid phase in the foam of the invention may have at least50% of its total crystallization enthalpy between 80° C. and −20° C.occurring in a temperature range between 40° C. and 15° C., for exampleat least 80% of its total crystallization enthalpy between 80° C. and−20° C. occurring in a temperature range between 40° C. and 15° C. Thelipid phase in the foam of the invention may have at least 50% of itstotal crystallization enthalpy between 80° C. and −20° C. occurring in atemperature range between 20° C. and −5° C., for example at least 80% ofits total crystallization enthalpy between 80° C. and −20° C. occurringin a temperature range between 20° C. and −5° C. Crystallizationenthalpy measurements may for example be measured by DSC.

The crystals comprising triglycerides occupying the surface of the gasbubbles in the foam according to the invention may form layers having anaverage thickness below 5 μm, for example between 0.2 and 5 μm. Thelipid crystals comprising triglycerides occupying the surface of the gasbubbles in the foam according to the invention may form layers having anaverage thickness below 2 μm, for example between 0.2 and 2 μm. Thelipid crystals comprising triglycerides occupying the surface of the gasbubbles in the foam according to the invention may form layers having anaverage thickness between 0.01 μm and 5 μm, for example between 0.05 μmand 2 μm, for further example between 0.2 μm and 1 μm. Thin layers ofcrystals provide an advantage as a smaller amount of crystals arerequired to wrap the bubbles and hence a smaller amount of highermelting components. As the bubble size in a foam decreases, for the samevolume of gas in the foam overall the surface area of the bubblesincreases, and so more crystals would be needed to coat the bubbles. Asthe invention provides gas bubbles coated with thin layers of crystals,foams with low densities can be formed with a small bubble size,providing interesting and attractive textures.

The foam of the invention does not rely on a rigid network in thecontinuous phase for its stability. This means that, at temperatureswhere a high proportion of the lipid phase is liquid, the foam is stableyet can be soft and flowable. Accordingly, the foam of the invention mayhave no rigid network in the continuous lipid phase at a temperature atwhich the lipid phase has a solid lipid content between 0.1 and 80%. Forexample the foam, at a temperature at which the lipid phase has a solidlipid content between 0.1 and 80% (for example between 0.1 and 60%, forexample between 0.5 and 40%, for example between 1 and 20%, for examplebetween 5 and 20%), may flow under gravity without losing more than 10%of its porosity (for example without losing more than 5% of itsporosity). A rigid network is present when flow induces partialinstability of the structure. On applying shear to a rigid network, asolid type of initial flow is observed. For example if a system having arigid network is sheared in a rheometer, an initial resistance ofelastic (or rigid) type would be observed, followed by a transitionthrough maximal resistance (breakage of the rigid structure) before thestructure would return to being flowable (at least in part). Thetransition is then not rapidly reversible (no rapid recovery of therigid network e.g. within a few seconds or minutes). This is in contrastto the behaviour of foams having no rigid network.

Most lipid materials used commercially are mixtures of differentmolecules. Vegetable and animal fats for example contain a range ofdifferent triglycerides. As a consequence, when cooling these fats, afraction of the triglycerides will start to crystallize while the restof the fat remains liquid. The inventors have found that by coolingliquid fats so that part of the triglycerides crystallize and a gelforms, and then aerating the gel, a stable foam may be produced. The gelstructure may continue to develop during and after foaming. Theinventors found for example that on cooling olive oil (80% refined, 20%extra virgin) to −23° C. a gel forms. After re-warming the gel byleaving at 5° C. for 3 hours, whipping the gel creates a stable foam(overrun around 65%) with gas bubbles having their surface occupied bytriglyceride crystals. For ease of processing, the temperature may beraised before whipping, as long as some crystals and the gel remain. Forexample the inventors were able to whip the olive oil gel at 5° C.,after solidifying it by cooling it to e.g. −10° C. and leaving it at−10° C. for a few hours, then leaving to partially melt at 5° C. beforewhipping. In such a foam, no additional stabilizer material needs to beadded to the liquid fat to enable a foam to be formed. Accordingly, inone embodiment of the invention, the lipid phase comprises one or morefats and the crystals comprising triglycerides occupying the surface ofthe gas bubbles comprise triglycerides from all the one or more fats.The fats may be vegetable fats. The fats may be selected from the groupconsisting of cocoa butter, olive oil, high stearic sunflower oil andcombinations of these. The composition of triglycerides occupyingsurface of the gas bubbles may be richer in higher melting triglyceridesthan the bulk fat. In the context of the current invention the termsoils and fats are used interchangeably. Conventionally in industry, theterm oils is used for fats which are liquid at the temperature at whichthey are traditionally sold. In another embodiment of the invention, oneor more higher melting-point fats may be included in the lipid phase ofthe foam to promote the formation of crystals to occupy the surface ofthe gas bubbles when the majority of the lipid phase is still liquid.The invention may provide a foam wherein the lipid phase comprises oneor more higher melting-point (HMP) fats and one or more lowermelting-point (LMP) fats and wherein the melting-point of the lowestmelting higher melting-point fat is at least 10° C., for example atleast 15° C., for example at least 20° C., above that of the meltingpoint of the highest melting lower melting-point fat and wherein thelower melting-point fats are present at a level of greater than 50 wt. %of the total lipid in the lipid phase, for example greater than 60 wt.%, for example greater than 70 wt. %, for example greater than 90 wt. %.A lipid phase composition as described facilitates the formation andstability of the foam, with crystals from the higher melting-point fatsoccupying the gas bubble surfaces while the lower melting-point fatsmaintain a fluid continuous phase to enable aeration, for example bywhipping.

Consider a lipid phase which consists of 6 wt. % high melting palm oilfraction (mpt. 63° C.), 40 wt. % cocoa butter (mpt. 35° C.) and 54 wt. %high oleic sunflower oil (mpt.—17° C.). The lipid phase has two HMP fats(high melting palm oil fraction and cocoa butter) and one LMP fat (higholeic sunflower oil). The melting point of the lowest melting HMP fat(cocoa butter) is 35° C., which is at least 10° C. above that of themelting point of the highest melting LMP fat, i.e. high oleic sunfloweroil with a melting point of −17° C. The LMP fat (HOSFO) is present at 54wt. % of the total lipid.

For different product applications and usage temperatures, the meltingpoints of the fats in the lipid phase may vary. The melting-point of thelowest melting HMP fat may be above 10° C., for example above 20° C.,for example above 30° C., for example above 40° C. A combination of asmall quantity of high melting fat with a large amount of low meltingfat can provide a stable foam at room temperature and below, which isparticularly beneficial for edible foams as they achieve stabilitywithout causing excessive waxiness in the mouth, and without an unwantedincrease in saturated fat content. For example, the melting-point of thelowest melting HMP fat may be above 40° C., for example between 40 and90° C., and the lower melting-point fats may be present at a level ofgreater than 90 wt. %. For example, the melting-point of the lowestmelting HMP fat may be above 30° C., for example between 30 and 50° C.,and the lower melting-point fats may be present at a level of greaterthan 75 wt. %. The crystals occupying the surface of the gas bubbles maycomprise triglycerides from the HMP fats. Fats present in minorquantities with melting-points between the temperature of the lowestmelting HMP fat and the highest melting LMP fats do not significantlyaffect the efficiency of foam formation. The melting-point of the lowestmelting higher melting-point fat may be at least 10° C., for example atleast 15° C., for example at least 20° C., above that of the meltingpoint of the highest melting lower melting-point fat when fats presentat levels below 1 wt. % of the lipid content of the lipid phase arediscounted. The melting-point of a fat may for example be thetemperature at which it has a 1% solid fat content as measured by pulsedNMR.

The one or more higher melting-point fats in the foam of the inventionmay be selected from the group consisting of cocoa butter, shea butter,kokum butter, illipe butter, sal fat, mango kernel fat, palm kernel oil,palm oil, coconut oil, milk fat, high stearic sunflower oil andhydrogenation products, inter-esterification products, fractions andcombinations of these; and the one or more lower melting-point fats maybe selected from the group comprising sunflower oil (high oleic andstandard), coconut oil, safflower oil, rapeseed oil, olive oil andcombinations and fractions of these. The one or more highermelting-point fats in the foam of the invention may have a melting pointabove 20° C. and the one or more lower melting-point fats in the foam ofthe invention may have a melting point below 20° C.

The higher melting-point fats in the foam of the invention may comprisecocoa butter, for example inter-esterified cocoa butter, and the lowermelting-point fats in the foam of the invention may comprise sunfloweroil, for example high oleic sunflower oil. The higher melting-point fatsin the foam of the invention may comprise a high melting fraction ofpalm oil, and the lower melting-point fats in the foam of the inventionmay comprise sunflower oil, for example high oleic sunflower oil. Thehigher melting-point fats in the foam of the invention may comprisehydrogenated coconut oil and the lower melting-point fats in the foam ofthe invention may comprise sunflower oil, for example high oleicsunflower oil. The higher melting-point fats in the foam of theinvention may comprise hydrogenated palm kernel oil and the lowermelting-point fats in the foam of the invention may comprise sunfloweroil, for example high oleic sunflower oil. The higher melting-point fatsin the foam of the invention may comprise shea butter, for examplefractionated or interesterified shea butter, and the lower melting-pointfats in the foam of the invention may comprise sunflower oil, forexample high oleic sunflower oil. The higher melting-point fats in thefoam of the invention may comprise illipe butter, for examplefractionated or interesterified illipe butter, and the lowermelting-point fats in the foam of the invention may comprise sunfloweroil, for example high oleic sunflower oil. The higher melting-point fatsin the foam of the invention may comprise high stearic sunflower oilstearin, and the lower melting-point fats in the foam of the inventionmay comprise high oleic sunflower oil.

Typically, lower melting fats have lower levels of saturated fatty acidsthan higher melting fats. Consumption of saturated fatty acids have beenlinked to increased levels of LDL cholesterol in the blood and heartdiseases and so it would be advantageous to be able to reduce theconsumption of saturated fatty acids. By being able to create a foamfrom a lipid phase with a high percentage of lower melting fats theinvention provides a means to reduce the saturated fatty acid content ofedible foams. The foam of the invention may be low in saturated fattyacids, for example the foam of the invention may have a saturated fattyacid content of less than 45 wt. % of the total fatty acid content, forexample less than 35 wt. % of the total fatty acid content, for exampleless than 25 wt. % of the total fatty acid content. The foam of theinvention provides an equivalent volume for less weight of material andhence reduces the total fat and therefore the saturated fatty acidcontent of any food product comprising it.

The inventors have found that the addition of particles may aid the foamstability, reducing coarsening over time and providing better foamhomogeneity. Solid particles having a particle size of less than 500 μmmay be dispersed in the foam. Particle size may be measured by themethods known in the art consistent with the size being measured. Forexample, a particle size less than 500 μm may be confirmed by passagethrough a standard US sieve mesh 35. The solid particles dispersed inthe foam may have a particle size less than 180 μm (e.g. measured bypassage through US mesh 80). The solid particles dispersed in the foammay have a D90 particle size measured by laser light scattering of lessthan 100 μm, for example less than 50 μm, for example less than 30 μm.The solid particles dispersed in the foam may be selected from the groupconsisting of modified starch, maltodextrin, inorganic salt (for exampleedible inorganic salt), protein particles, fibres (for example slowlydigestible or digestion resistant carbohydrates), plant particles (forexample cocoa particles, coffee particles, spices or herbs), sugars (forexample sucrose), hydrogel particles and combinations of these. Thesolid particles dispersed in the foam may be maltodextrin. The solidparticles may be present at a level of between 1 and 500% of the totallipid weight in the foam, for example between 1 and 200% of the totallipid weight in the foam, for example between 1 and 100% of the totallipid weight in the foam, for example between 1 and 20% of the totallipid weight in the foam, for further example between 5 and 20% of thetotal lipid weight in the foam.

The foam of the invention may be comprised within a food product orcosmetic product. For example the foam of the invention may be a foodproduct; for example an aerated dressing or sauce (sweet or savoury); anaerated dairy product such as a mousse dessert; an aerated beverage orbeverage enhancer; or an aerated nutritional formula (for example anutritional formula for dysphagia patients which is easier to swallow).Incorporating a gas such as air into a food product can be used tocreate an attractive texture and also provides a means to reduce the fatcontent of a food without reducing its volume. The foam may be generatedat the point-of-sale, for example to provide a topping for a beverage orice cream. The foam of the invention may be a cosmetic product, forexample a foamed massage oil (such as foamed baby oil) or an aeratedskincare cream. The foam of the invention may be comprised within a petfood or a bakery product (such as added to a bakery dough for example asan aerated biscuit shortening).

In a further aspect, the invention provides a process for forming afoam, the process comprising the steps of providing a compositioncomprising triglycerides and having a lipid content greater than 20 wt.% (for example greater than 30 wt. %, for example greater than 40 wt. %,for example greater than 50 wt. %, for example greater than 60 wt. %);controlling the temperature of the composition such that the compositioncomprises triglyceride crystals, has a solid lipid content between 0.1and 80% (for example between 0.1 and 60%, for example between 0.5 and40%, for example between 1 and 20%, for example between 5 and 20%), andforms a gel; and aerating the gel to form a foam. The foam may comprisegas bubbles having their surface occupied by crystals comprisingtriglycerides. In the context of the present invention the term aeratingrefers to foaming by the incorporation of gas bubbles, the gas notnecessarily being air. Aeration may be achieved by any of the techniquesknown in industry, for example mechanical agitation, passive mixing(e.g. passing through slit or nozzle), pressure drop (e.g. to vacuum, orfrom elevated pressure to atmospheric pressure) or sparging (when achemically inert gas is bubbled through a liquid).

A gel is a non-fluid network characterised by a continuous liquidthroughout its whole volume. The gel of the process of the invention mayhave a continuous lipid phase. The gel of the process of the inventionmay have a gel property arising from a crystal network, for example anetwork of crystals of average size below 100 microns throughout thematrix. The gel of the process of the invention may have between 3 and30% of the total lipid by weight in the form of crystals, for examplebetween 5 and 20%. A gel may be defined by its rheology. For example ata frequency of 1 Hz, the measured linear shear elastic modulus G′ of agel may be greater than 10 Pa and the viscous modulus G″ may be lessthan G′. Gels most suitable for foam generation have a linear shearelastic modulus G′ initially in the range 10²-10² Pa at 1 Hz, forexample a linear shear elastic modulus G′ initially in the range 10²-10⁶Pa at 1 Hz, for further example a linear shear elastic modulus G′initially in the range 10³-10⁶ Pa at 1 Hz.

The composition comprising triglycerides may comprise a range ofdifferent triglycerides with different melting points. Thecrystallization behaviour of the composition comprising triglyceridesmay be examined using differential scanning calorimetry (DSC). Aerationmay be performed at a temperature below the highest melting peakmaximum, the temperature being such that the solid lipid content isbetween 0.1 and 80%, preferably at a temperature below the whole peakarea of the highest endothermic melting peak. For example, in a mixtureof 20% cocoa butter in high oleic sunflower oil, the highest meltingpeak was found to have a maximum at 23° C. Good results were obtained byaerating the mixture which had been recently cooled to a temperature of17° C., the solid lipid content being between 0.1 and 80%.

The composition comprising triglycerides in the process of the inventionmay comprise one or more higher melting-point (HMP) fats and one or morelower melting-point (LMP) fats wherein the melting-point of the lowestmelting higher melting-point fat is at least 10° C., for example atleast 15° C., for example at least 20° C., above that of the meltingpoint of the highest melting lower melting-point fat and wherein thelower melting-point fats are present at a level of greater than 50 wt. %of the total lipid in the lipid phase, for example greater than 60 wt.%, for example greater than 70 wt. %, for example greater than 90 wt. %.

Solid particles having a particle size of less than 500 μm, for exampleless than 180 μm, may be added to the composition comprisingtriglycerides in the process of the invention. The solid particles mayhave a D90 particle size of less than 100 μm, for example less than 50μm, for example less than 30 μm. The solid particles may be added beforethe composition forms a gel. The solid particles added to thecomposition comprising triglycerides may be selected from the groupconsisting of modified starch, maltodextrin, inorganic salt, proteinparticles, fibres, plant particles, sugars, hydrogel particles andcombinations of these. The solid particles may have been ground oraggregated. The solid particles added to the composition comprisingtriglycerides may be maltodextrin. The solid particles may be present ata level of between 1 and 20% of the total lipid weight in the foam.

Cooling the triglyceride composition will promote the formation ofcrystals. This can be enhanced by the addition of small crystals, forexample crystals of a higher melting fat. The added crystals maythemselves occupy the surface of the gas bubbles when the gel isaerated, or they may promote the growth of crystals which occupy thesurface of the gas bubbles or a mixture of both. Accordingly,triglyceride crystals may be added to the composition comprisingtriglycerides in the process of the invention, for example they may beadded whilst controlling the temperature of the lipid composition.

The composition comprising triglycerides may initially be at atemperature at which it contains less than 0.1 wt. % solid lipid in theprocess of the invention. For example it may be at a temperature atwhich it contains no solid lipid. Starting with less than 0.1 wt. %solid lipid, or no solid lipid, makes it easier to control theconditions such that a proportion of the composition comprisingtriglycerides crystallizes, providing suitable crystals for occupyingthe surface of gas bubbles in the foam generated by the process of theinvention.

The inventors have found that improved results (e.g. lower density foamsand greater stability) may be obtained if the gel is allowed to maturebefore being aerated. There may be a time interval of at least 5 minutesbetween the formation of the gel and the start of the aeration in theprocess of the invention. The time interval between the formation of thegel and the start of the aeration in the process of the invention may beat least 30 minutes, for example at least 1 hour, for example at least24 hours, for example at least 4 weeks. At long maturation times, thestability of the foam increases with maturation time but the densitystarts to decrease. The time interval between the formation of the geland the start of the aeration in the process of the invention may bebetween 1 hour and 2 weeks, for example between 1 hour and 1 week, forfurther example between 1 hour and 24 hours. The gel may be maintainedat any temperature during the time between formation of the gel and thestart of the aeration as long as the composition maintains a solid lipidcontent between 0.1 and 80%. The inventors have found that the higherthe temperature of the gel when it is whipped, the lower the density offoam obtained, providing the temperature is not raised to the point thatall triglyceride crystals melt and the gel is destroyed. For example,the composition comprising triglycerides may be cooled rapidly, such asin a freezer at −18° C. to form a gel, and then allowed to warm up to atemperature at which only a few percent solid lipid remains before beingaerated.

The aeration step in the process of the invention may comprisemechanical agitation, for example whipping. The inventors have foundthat although foams could be obtained by non-mechanical agitationmethods, such as dissolving or dispersing gas under pressure and thenreleasing it, to obtain the most stable foams it was preferable to applymechanical agitation. Without wishing to be constrained by theory, theinventors believe that mechanical agitation increases the wrapping ofthe gas bubbles with triglyceride crystals. Mechanical agitation may forexample be applied using rotor-stator type of equipment, such as aHaas-Mondomix aerating system. After formation, and maturation (if any),the gel may be gently sheared to allow an easy transfer to the aeratingsystem. Mechanical agitation, for example whipping, may be applied forat least 5 s (such as the residence times in a continuous rotor-statorsystem), for example at least 1 minute, for example at least 5 minutes(such as in a batch whipping machine), for example at least 10 minutes,for further example at least 30 minutes. Foam stability generallyincreases with increasing mechanical agitation time. In contrast to manyfoams, the foam generated according to the process of the invention isnot particularly sensitive to over-whipping. The aeration step in theprocess of the invention may comprise gas depressurization followed bymechanical whipping. Such a combination of initial bubble generationusing dissolved/dispersed gas and a pressure drop followed by mechanicalagitation may usefully be employed, however all process steps may beperformed at or near atmospheric pressure, for example at an absolutepressure of between 800 hPa and 2100 hPa, for example between 850 hPaand 1100 hPa.

The process of the invention may further comprise adding additionalmaterials. For example the process may include adding additional foodingredients and forming a food product. The process may include addingadditional materials before the formation of the gel, after a gel isformed or to the foam.

The foam obtained in the process of the invention by aerating the gelmay be mixed with un-aerated composition, for example the foam may bemixed with an un-aerated composition having a lipid continuous phase.Such a “two-step” process is particularly effective at creating anaerated composition having a low lipid content when the foam obtained inthe process of the invention has a lipid content higher than theun-aerated composition. Lipid-continuous compositions with low lipidcontents are difficult to aerate, as the foam structure tends to breakduring whipping. The inventors were surprised to find that by creating afoam according to the process of the invention using a composition witha high lipid content and then carefully mixing the foam with anun-aerated material with a lower fat content they could obtain muchhigher porosity than could be obtained by whipping the final compositiondirectly. Without wishing to be bound by theory, the inventors believethat the formation of crystal-wrapped bubbles in the initial foamprovides a foam with good stability during mixing, allowing it to bemixed into un-aerated material with very little loss of porosity.

In an embodiment of the process of the invention, the lipid phase of thecomposition comprising triglycerides may have at least 80% of its totalcrystallization enthalpy between 80° C. and −20° C. occurring in atemperature range of at least 20° C., for example a range of at least30° C. In an embodiment of the process of the invention the lipid phaseof the composition of the invention may have at least 50% of its totalcrystallization enthalpy between 80° C. and −20° C. occurring in atemperature range between 40° C. and 15° C., for example at least 80% ofits total crystallization enthalpy between 80° C. and −20° C. occurringin a temperature range between 40° C. and 15° C. In a further embodimentof the process of the invention the lipid phase of the composition ofthe invention may have at least 50% of its total crystallizationenthalpy between 80° C. and −20° C. occurring in a temperature rangebetween 20° C. and −5° C., for example at least 80% of its totalcrystallization enthalpy between 80° C. and −20° C. occurring in atemperature range between 20° C. and −5° C.

The process of the invention may comprise the steps of providing acomposition comprising triglycerides and having a lipid content greaterthan 40 wt. %; controlling the temperature of the composition such thatthe composition comprises triglyceride crystals, has a solid lipidcontent between 0.1 and 80% (for example between 0.1 and 60%, forexample between 0.5 and 40%, for example between 1 and 20%, for examplebetween 5 and 20%), and forms a gel; aerating the gel to form a foam;and mixing the foam with an un-aerated lipid-continuous compositionhaving a lipid content lower than 40 wt. % to form a further foam. Thefurther foam formed by mixing the initial foam with an un-aeratedlipid-continuous composition may have a lipid content below 40 wt. %,for example below 35 wt. %, for further example below 30 wt. %. Thefoams may comprise gas bubbles having their surface occupied by crystalscomprising triglycerides. In the context of the present invention, theterm “un-aerated” refers to a composition having a porosity below 1%,for example the un-aerated lipid-continuous composition may have aporosity in the lipid phase of less than 1%.

The temperature of the composition comprising triglycerides may becontrolled to form a gel, for example by rapid cooling, and then furtheringredients mixed in, acting to increase the temperature of the gelready for efficient aeration, but without melting out all the solidlipid content. It is an advantage of the process of the invention thatit provides a foam with good stability such that additional ingredientsmay be mixed into the foam without leading to too great an increase indensity. The foam may be allowed to mature before additional ingredientsare added. For example the time interval between the formation of thefoam and the addition of further ingredients, for example foodingredients, may be at least 30 minutes, for example at least 1 hour,for example at least 24 hours, for example at least 4 weeks.

In an embodiment of the process of the invention, the process maycomprise the steps of providing a composition comprising triglycerideshaving a cocoa butter content between 5 and 50% by weight (for examplebetween 15 and 25% by weight) and a lower melting-point fat contentbetween 50 and 95% by weight (for example between 85 and 50% by weight),wherein the lower melting-point fat has a highest melting point below 0°C. (for example below −10° C.); cooling the composition to a temperaturebetween 0 and 15° C. such that the composition comprises triglyceridecrystals, has a solid lipid content between 0.1 and 80% (for examplebetween 5 and 20%) and forms a gel; and aerating the gel (for example bymechanical whipping) to form a foam. The composition comprisingtriglycerides may be free from lipid crystals before being cooled. Theresulting foam may optionally be mixed with an un-aeratedlipid-continuous composition.

In a further embodiment of the process of invention, the process maycomprise the steps of providing a composition comprising triglycerideshaving a higher melting-point fat content between 5 and 50% by weight(for example between 15 and 25% by weight) and a lower melting-point fatcontent between 50 and 95% by weight (for example between 50 and 85% byweight), wherein the higher melting-point fat has a lowest melting pointabove 30° C. (for example above 35° C., for further example above 40°C.) and the lower melting-point fat has a highest melting point below10° C. (for example below 0° C., for further example below −10° C.);cooling the composition to a temperature between 0 and 25° C. (forexample between 0 and 15° C.) such that the composition comprisestriglyceride crystals, has a solid lipid content between 0.1 and 80%(for example between 5 and 20%) and forms a gel; and aerating the gel(for example by mechanical whipping) to form a foam. The compositioncomprising triglycerides may be free from lipid crystals before beingcooled. The resulting foam may optionally be mixed with an un-aeratedlipid-continuous composition.

Those skilled in the art will understand that they can freely combineall features of the present invention disclosed herein. In particular,features described for the product of the present invention may becombined with the process of the present invention and vice versa.Further, features described for different embodiments of the presentinvention may be combined. Where known equivalents exist to specificfeatures, such equivalents are incorporated as if specifically referredto in this specification. Further advantages and features of the presentinvention are apparent from the figures and non-limiting examples.

Examples Example 1: Formation of Stable Foams with Cocoa Butter in HighOleic Sunflower Oil

High Oleic Sunflower Oil (HOSFO) having a melting point of −17° C. (±3°)C. was obtained from (SABO Nestrade). Cocoa butter (Pure Prime Pressed)having a melting point of 35° C. (±3°) C. was obtained from Cargill.

The melting and crystallizing profile of 20 wt. % cocoa butter in HOSFOwas measured by DSC using a SDT Q600 from TA instruments. A sample ofaround 10-20 mg of cocoa butter in HOSFO was heated to 70° C. beforerecording the crystallization signature. After cooling to −20° C., itwas reheated to 70° C. to record the melting signature. The DSC trace isshown in FIG. 1. It can be seen that the highest melting peak has a peakmaximum at about 23° C. and the peak starts at around 17° C. Althoughdifferent lipids and crystalline forms may have slightly differentspecific melting enthalpies, the area under the melting peaks in thereheating trace provides a reasonable correlation with the quantity oflipid melting. From the DSC reheating trace it can be seen that by 5° C.less than 60% of the lipid remains solid.

The formation of a gel was confirmed. FIG. 2 shows the evolution of G′(●) and G″ (▪) with time (sec), recorded at 1 Hz, for 20% cocoa butter(PPP) in HOSFO cooling down from 25° C. to 5° C. (♦) and stabilizing at5° C., with a cooling rate of 0.5° C./min. The strain amplitude was keptat 0.005% to ensure to be in the linear deformation regime. Geometryused was concentric cylinders. Gelation profile of 20% cocoa butter inHOSFO as temperature was lowered from 25° C. to 5° C. The mixture wasinitially heated up to 70° C. for achieving complete dissolution, thenthe temperature was lowered to 25° C. within ½ hour prior to recordingrheological data during gelation. It can be seen that after 45 minuteswhen the gel forms, G′ is greater than G″ and G′ is greater than 10 Pa.

1.1 Gel at 4° C., Whipping at 20° C.

Mix preparation: 20% (w/w) cocoa butter in HOSFO was heated to 70° C.until complete dissolution. 250 g of the heated solution was placed in adouble-jacketed glass container. The mixture was cooled down over 20hours by applying water at 4° C. to the jacket. The gel obtained wasplaced at 20° C. in a Hobart N50 planetary kitchen mixer fitted with aballoon whisk at speed 2 for 15, 30, 45 min. A foam with an overrun of240% was obtained. (Overrun is the volume of gas incorporated into thefoamed material/volume of the un-foamed material, expressed in %.) Thebubble size distribution was wide, with an average size estimated in therange 0.02-0.05 mm, but with only a very small fraction (less than 5%)of bubbles larger than 0.1 mm. The foam had good stability at lowtemperatures, but if maintained at room temperature it collapsed over 1hour.

1.2 Gel at 4° C., Whipping at 5° C.

The protocol was same as 1.1 above except that the whipping wasperformed at 5° C. by placing the kitchen mixer in a cold room. A highoverrun foam was achieved (200% after 15 minutes whipping). Bubble sizedistribution was wide, with an average size estimated in the range0.03-0.05 mm, but with only a very small fraction (less than 5%) ofbubbles larger than 0.1 mm. The foam had good stability at lowtemperatures, but if maintained at room temperature after foaming, thefoam showed around 1 cm of drainage after 7 days of storage at roomtemperature (see FIG. 3). The texture of the foam was much firmer andless prone to flow than that of the gel before whipping.

1.3 Gel Held at 5° C. for 1 Week—Foaming at 5° C.

The protocol was the same as 1.1 above, except that 250 g of the mix wasstored at 5° C. for 1 week, which allowed for recrystallization. The gelwas then whipped at 5° C. for 15 min, 30 min and 45 min. A high overrunfoam was achieved (180% after 15 minutes whipping and 235% after 30minutes whipping). Average bubble size was smaller than in the earliertrials, estimated to be 0.03-0.05 mm, leading to very white appearanceof foam. Foam showed a better stability at room temperature, i.e. itcould be stored for weeks without apparent macroscopic collapse, andwith very limited drainage (below 1 mm of drainage after 7 days ofstorage) (see FIG. 4).

1.4 Gel Held at 5° C. for 1 Week—Foaming at 20° C.

The protocol was the same as in 1.3 above except that whipping wasperformed at 20° C. A high overrun foam was achieved (225% after 15minutes). Stability and bubble size was similar to 1.3.

1.5. Gel Held at 5° C. for 2 Weeks—Foaming at 5° C.

The protocol was same as in 1.3 except the gel storage duration whichwas 2 weeks. The stability and bubble size was similar to 1.3.

Summary of Results Foaming 20% Cocoa Butter in High Oleic Sunflower Oil:

Conditions Max overrun Gel 4° C. - Foamed at 20° C. 243% Gel 4° C. -Foamed at 5° C. 245% Gel held at 5° C. for 1 week. Foamed at 5° C. 235%Gel held at 5° C. for 2 weeks. Foamed at 5° C. 200% Gel held at 5° C.for 1 week. Foamed at room temperature 226%

Example 2: Foams with Cocoa Butter in High Oleic Sunflower Oil withAddition of Maltodextrin Particles

Mix preparation: 20 wt. % cocoa butter, 10 wt. % maltodextrin particles(DE11-14) in HOSFO was heated to 70° C. until complete dissolution ofthe cocoa butter. 250 g of the mix placed in a closed vial. The vial wasplaced in water, cooled within a double-jacketed container (coolingwater at 4° C.) for 20 hours. The gel obtained was stored at 5° C. for 1week before being placed in a Hobart kitchen mixer at 5° C. fitted witha balloon whisk and whipped at speed 2 for 15 min, 30 min and 45 min.The resulting foam was compared with trial 1.3 above which had the sameconditions apart from no maltodextrin particles. The foam withmaltodextrin particles has a maximum overrun of 214% (compared to 235%for the sample with no particles). However, the trial with maltodextrinhad improved stability against coarsening over time and showed betterhomogeneity of the foam.

Example 3: Foaming of Other Fats at 20 wt. % in High Oleic Sunflower Oil

A series of other fats were prepared at 20 wt. % in high oleic sunfloweroil, being completely melted and then cooled to a gel. The samples werewhipped as in example 1.

Max overrun & Fat Conditions comments Refined hydrogenated Gel stored at15° C. 187% coconut oil, Mpt. for 15 h, then at 5° C. Poor storage at38° C. (Peerless for 1 h. Whipped at 20° C., but good Foods, Australia)5° C. at 5° C. Hydrogenated palm Gel stored at 15° C. 177% kernel oil,Mpt. for 15 h, then at 5° C. Stable at 20° C. 45° C. (Lam Soon, for 2 h.Whipped at without drainage Thailand) 5° C. after 7 days but with somecontraction Cocoa Butter Gel stored at 15° C. 264% equivalent, Mpt. for15 h, then at 5° C. Stable at 20° C. 45° C. (Loders for 20 h. Whipped atwithout drainage Croklaan) 5° C. after 7 days High melting palm Gelstored at 20° C. 141% fraction, Mpt. for 16 h, then at 5° C. Stable at20° C. 60° C. (AAK for 1 h. Whipped at without drainage Sweden) 5° C.after 7 days Interesterified Gel stored at 5° C. 75% cocoa butter, for 5h, then at 5° C. 1 cm drainage Mpt. 52° C. for 1 h. Whipped at after 7days at (Cargill) 5° C. 20° C.

Example 4: Foaming of Single Oil

High stearic sunflower oil stearin (Nutrisun) is a high melting fractionof sunflower oil. Melting point 32° C. (±3° C.).

The high stearic sunflower oil stearin was heated to 90° C. to ensurecomplete dissolution of crystals. 250 g of the heated solution wasplaced in a double-jacketed glass container. The mixture was cooled downover 20 hours by applying water at 20° C. to the jacket. The gelobtained was placed in a Hobart kitchen mixer fitted with a balloonwhisk at speed 2 for 15 min. High overrun foam was made (maxoverrun=277% after 45 min whipping). This foam showed good heatstability without apparent macroscopic destabilization and withoutapparent drainage after 7 days of storage.

Bubble size distribution was very wide, with an average size estimatedin the range 0.06-0.08 mm, but with only a very small fraction (lessthan 5%) of bubbles larger than 0.1 mm. This demonstrates that foams maybe produced from single fats (for example vegetable fats from a singleplant source), the crystals occupying the surface of the gas bubblesnecessarily coming from the same fat.

Example 5: Bubbles Coated by Crystals

FIG. 5 shows the dense layer of crystals absorbed at the surface ofbubbles in a micrograph of the cocoa butter/high oleic sunflower oilfoam formed in trial 1.5 above. The image illustrates the type ofnon-spherical shapes that are found under the microscope, wherebyinterfacial stabilization by surface adsorption of a dense layer ofcrystals creates the property of the non-relaxing shape (showndiagrammatically in FIG. 6). By diluting the foam with liquid oil (e.g.the same liquid oil used for foaming) the bulk rheological effectsnormally acting on bubble shape are suppressed, but the interfacialstabilization of the crystals around the bubbles can be observed by thefact that the bubble shapes do not relax. From microscopicalobservations of these foams, around 50% of bubbles were found to have asurface coverage at least 50% of the maximal surface coverage. Maximalsurface coverage corresponds to a jammed structure of crystals adsorbedat a bubble's interface, or at the interface between two bubbles. Thedense packing of crystals at bubble interfaces gives good stability.

A high melting palm oil fraction (AAK, Sweden) was foamed in HOSFO andthe structure studied by microscopy. Mix preparation: 20% high meltingpalm oil fraction was dissolved in HOSFO by heating to 75° C. A gelformed during storage at 20° C. for 16 h. 250 g of the gel obtained wasplaced in a Hobart kitchen mixer and whipped at speed 2 for 45 minutes.FIG. 7 shows a polarized micrograph of the foam not diluted, and thenFIG. 8 shows the foam diluted by a factor of around 5 with HOSFO. Themicrographs show triglyceride crystals coating the interfaces betweenbubbles.

Example 6: Foams Stabilized by Triglyceride Crystals—Visualization ofthe Adsorbed Triglyceride Crystals at Interface by Optical Microscopy

HOSFO and 10 wt % cocoa butter improver (CBI) were mixed at 60° C. untilcomplete dissolution. The CBI (Illexao HS90—AAK) is based onfractionated shea butter and has a melting point of 43° C.±3° C. TheHOSFO/CBI mixture was removed from the hot plate and left to coolovernight at 5° C. The mixture formed a gel with a paste-likeconsistency. Foam was generated in a Hobart mixer with balloon whisk,speed 2, for 20 min at 5° C. During whipping, air is incorporated intothe gel matrix and forms bubbles coated by crystals that ensurelong-term mechanical stability to the foam.

The samples were examined using optical microscopy. A few drops of theaerated material was placed onto a glass slide and then imaged usingappropriate magnification and brightfield illumination using a Zeissoptical microscope. The images (FIGS. 9 and 10) clearly show a completelayer of crystals adsorbed at the air/oil interface and forming a crustwrapping the bubbles. With such a high level of surface coverage it isimmediately obvious after inspection by microscopy that at least 50% ofthe surface of the gas bubbles is occupied by crystals.

Example 7: Forming a Milk-Chocolate Based Foam—1-Step Versus 2-StepProcess

An aerated milk chocolate was formed using three different glyceridematerials to stabilize the oil foam: a CBI as in example 18, a CBE as inexample 3 and monoglycerides as in example 6. For the CBI andmonoglycerides, a 1-step process was compared with a 2-step process.

Foaming in 1 Step:

10% glyceride material (CBI or monoglycerides) was mixed with 90% oil(high oleic sunflower oil, HOSFO) and heated until no solids remained.This oil mixture was cooled to 20° C. in a water bath, and maintained atthat temperature. The oil mixture formed a gel.

A milk chocolate with 34% fat was fully melted and then cooled down to30° C. The chocolate was tempered by seeding; 0.2% of Chocoseed A (Fuji)was gently mixed in, ensuring no incorporation of air.

The oil mixture (20%) was combined with the chocolate (80%) and whippedin a Hobart mixer, the temperature being maintained at 30° C. Theoverrun increased up to a whipping time of 1 hour.

Foaming in 2 Steps:

10% glyceride material (CBI, CBE or monoglycerides) was mixed with 90%oil (HOSFO) and heated until no solids remained. This oil mixture wascooled to 20° C. in a water bath, and maintained at that temperature.The oil mixture formed a gel.

A milk chocolate with 34% fat was fully melted and then cooled down to30° C. The chocolate was tempered by seeding; 0.2% of Chocoseed A (Fuji)was gently mixed in, ensuring no incorporation of air.

The oil mixture was whipped at 20° C. in a Hobart mixer to form a whitefoam. The white foam was then gently mixed into the chocolate with aspatula.

The porosities for the aerated milk chocolates obtained are shown below.

Glyceride used 1-step 2-step Monoglycerides 0.16 0.26 CBI 0.30 0.38 CBE— 0.37

The 2-step process, where an aerated gel is mixed with an un-aeratedcomposition, resulted in higher porosities. Crystals surrounding the airbubbles could be observed in all samples by microscopy, for example FIG.11 which shows the CBE oil foam.

The foams obtained using monoglycerides were examined after 20 daysstorage. The 1-step foam was found to be darker in colour (indicating alower air content) and, when disturbed, the 1-step foam collapsed morereadily. Microscopical observations of the two foams showed that only afew gas bubbles remained in the 1-step foam, and these were mostly largebubbles. The 2-step foam in contrast had a much greater number ofbubbles, the bubbles being smaller in size.

Example 8: Biscuit Recipe

A biscuit was prepared using an oil foam to partially replace the fat inthe biscuit dough. The reference biscuit was prepared from 140 g meltedmilk butter, 140 g white, 110 g brown sugar, 1 egg, 1 teaspoon ofvanilla extract, 240 g of flour, 6 g of chemical yeast, 6 g of Na₂CO₃,80 g of nuts, 200 g of chocolate (broken into small pieces). Allingredients were mixed together into a dough with the melted butterbeing added last. The dough was split into 5-10 cm diameter balls andbaked for 15 min. at 75° C.

The oil foam biscuit was prepared in a similar manner, but 50% of thebutter by volume was replaced by an oil foam. This led to approximately70 g of butter being replaced by 20 g of the oil foam. The foam wasprepared as follows: 10 wt. % of cocoa butter improver (IllexaoHS90—AAK), was mixed with HOSFO and warmed until no solid remained. Themixture was placed at 4° C. until it formed a gel (approx. 5 hours) andthe gel was then whipped (also at 4° C.) for 1 hour using a kitchenmixer (Hobart, Switzerland) equipped with a balloon whisk. The foam wasvery stable at 4° C. with no drainage observed. The overrun was between240-260 vol %, the porosity was therefore between 70 and 72. The oilfoam was gently mixed into the other dough ingredients before the meltedbutter.

Further oil foam biscuits were prepared in the same way but with a cocoabutter equivalent (Coberine®—IOI Loders Croklaan) instead of the cocoabutter improver.

The reference and the oil foam recipes produced acceptable biscuits,with the oil foam biscuits containing less fat by volume.

Example 9: Cake Recipe

A sponge cake was prepared using an oil foam to partially replace thefat in the cake batter. The reference cake was prepared from 500 g eggwhites, 350 g caster sugar, 350 g flour, the zest and juice of a lemonand 100 g butter. The egg whites were whipped together with the sugar toobtain a firm foam. The flour was then sifted over the egg mixture andgently folded together before adding the lemon. Finally, the meltedbutter was folded into the mixture to form a cake batter. The batter wasplaced in a baking tin and baked at 180° C. for 45 minutes. For the oilfoam version, an oil foam was prepared as in example 21. 50% of thebutter by volume was replaced by the oil foam in the recipe. This led to50 g of butter being replaced by approximately 29 g of the oil foam. Theoil foam was gently mixed into the other cake ingredients before themelted butter.

Further oil foam cakes were prepared in the same way but with a cocoabutter equivalent (Coberine®—IOI Loders Croklaan) instead of the cocoabutter improver.

The reference and the oil foam recipes produced acceptable cakes. Intechnical tasting the reference cake and the oil foam versions werefound to be very similar.

1-15. (canceled)
 16. A foam having a continuous lipid phase and aporosity between 1 and 80% wherein, at a temperature at which the lipidphase has a solid lipid content between 0.1 and 80%, the foam comprisesgas bubbles having at least 50% of their surface occupied by crystalscomprising triglycerides.
 17. The foam according to claim 16, whereinthe crystals comprising triglycerides occupying the surface of the gasbubbles form layers having an average thickness below 5 μm.
 18. The foamaccording to claim 16, wherein the lipid phase comprises one or morefats and the crystals comprising triglycerides occupying the surface ofthe gas bubbles comprise triglycerides from all the one or more fats.19. The foam according to claim 16, wherein the lipid phase comprisesone or more higher melting-point fats and one or more lowermelting-point fats and wherein the melting-point of the lowest meltinghigher melting-point fat is at least 10° C. above that of the meltingpoint of the highest melting lower melting-point fat and wherein thelower melting-point fats are present at a level of greater than 50 wt. %of the total lipid in the lipid phase
 20. The foam according to claim19, wherein the one or more higher melting-point fats are selected fromthe group consisting of cocoa butter, shea butter, illipe butter, salfat, kokum butter, mango kernel fat, palm kernel oil, palm oil, coconutoil, milk fat, high stearic sunflower oil and hydrogenation products,inter-esterification products, fractions and combinations of these; andthe one or more lower melting-point fats are selected from the groupcomprising sunflower oil, coconut oil, safflower oil, rapeseed oil,olive oil and combinations and fractions of these.
 21. The foamaccording to claim 16, wherein solid particles having a particle size ofless than 500 μm are dispersed in the foam.
 22. The foam according toclaim 21, wherein the solid particles are selected from the groupconsisting of modified starch, maltodextrin, inorganic salt, proteinparticles, fibres, plant particles, sugars, hydrogel particles andcombinations thereof.
 23. The foam according to claim 16, wherein thetriglycerides are more than 95 wt. % of the total lipids of the foam,and all fatty acids in the triglycerides have a carbon chain length lessthan 22, and the foam contains less than 5 wt. % of water.
 24. The foamaccording to claim 16, having a solid lipid content between 5% and 20%,and the foam is a gel having a linear shear elastic modulus G′ of10²-10⁷ Pa at 1 Hz.
 25. The foam according to claim 16, wherein the foamdoes not have a rigid network of crystals between the bubbles.
 26. Aproduct comprising a foam comprising a continuous lipid phase and aporosity of between 1 and 80% wherein, at a temperature at which thelipid phase has a solid lipid content between 0.1 and 80%, the foamcomprises gas bubbles having at least 50% of their surface occupied bycrystals comprising triglycerides, wherein the product is a food productor a cosmetic product.